1. Field of the Invention
The present invention relates to a method of processing waste material, and more particularly to a method of processing waste material that is contaminated with, for instance, mercury compounds.
2. Description of the Related Art
Known conventional methods for disposing of mercury-containing waste material by incineration involve using washing towers or activated carbon filters for treating the mercury. In washing tower methods mercury must be washed by being converted into mercury chloride (II), which is a water-soluble compound. A supplementary process is therefore required for this conversion. Although the mercury recovery rate in this treatment method is as high as 90% and is comparatively high, the conversion product, mercury chloride (II), is highly toxic. Mercury and chlorine bind easily to each other, to form readily mercury chloride (II) that is soluble in water and ethanol. This is problematic in that the mercury must be recovered once more from the washing water in which the mercury chloride (II) had been recovered. Meanwhile, methods that employ activated carbon filters are likewise problematic in that effective mercury recovery is difficult, and 100% mercury recovery cannot be achieved. Other recovered mercury compounds besides mercury chloride (II) may also be toxic, depending on the form of the mercury compound in question.
Further conventional methods that have been proposed involve the use of adsorbents for treating toxic substances, such as dioxines, that are generated in waste incinerators. Disclosed methods for regenerating spent adsorbents, in the case where the spent adsorbent used for toxic substance removal contains mercury, involve subjecting the mercury-containing spent adsorbent to a thermal treatment in a nitrogen atmosphere at an atmosphere temperature of 300° C., to remove mercury and the like from the adsorbent into a gas (for instance, Japanese Patent. Application Laid-open No. 2000-167395). The treatment method disclosed in Japanese Patent Application Laid-open No. 2000-167395, however, has a problem that the mercury removed from the adsorbent cannot be recovered efficiently and safely from the gas.